Method of fumigation



Patented July 9, 935 2 07 73 UNITED STATES PATENT OFFICE John Baer, Chicago, 11]., asslgnor to The Gllardite Corporation, a corporation of Illinois Application January 22, 1934, Serial No. 707,810

' B CIaims. (Cl. 99-9) This invention relates to an improved method means for heating the vapors, as for example of fumigation, and particularly to the fumigaa steam coil I. tion of vegetable products with a mixture of va- In carrying out the process the tank 2, conpors from volatile liquids. taining the liquids, the vapors of which are to In carrying out fumigation of ,food or other he used as fumigants, is connected to the ac- 5 vegetable and animal products, a mixture of vacumuleter- If mmi q i W not mix pors i customarily supplied. The vapors are within the tank; but the lighter will float upon taken from the liquids, which are supplied in the heavier. In carrying out the invention, subtanks under pressure. Generally the fumigant stantially the entire contents of the liquid tank 2 comprises carbon dioxide or other inert gas such are then evap rated in h ul r 3, 01 10 as nitrogen or the like, together with a minor until the pressure in the two are substantially proportion of toxic gas such as ethylene oxide, equal, and are mixed within the accumulator to methyl formate or the like. For example, a form a. homogeneos mixture before admission to preferred fumigant'comprises 9 parts by weight the fumigator. After thoroughly mixing in the of carbon dioxide and 1 part by weight of ethylene accumulator, du g w h time the gases are 15 oxide. preferably heated to a temperature of the order In commercial practice, the fumigating mateof 120 F., they may be admitted to the fumigator. rials are supplied in liquid form, the liquids be- In the pr f d method f fu ati n. t ing placed in the desiredproportion under high products to be fumigat'ed are placed within the pressure in a steel tank. The liquids commonly fumigator 5, which is evacuated to a pressure of 2 used may not be miscible in the proportions used. A1" of mercury absoluteor less, and the fumigat- On this account removal of vapors in the proing gases are then admitted and the total gas portions in which the liquids are present is not pressure brought up thereby to 15-20" of mercury possible under present methods. If the outlet absolute. The gases are maintained at a conis from the bottom of the tank the heavier siderable pressure in the accumulator 3, for ex- 25 liquid comes oil first, whereas if vapors are reample, 75 lbs., and it is found that there is no moved from the top, the more volatile comes ofi separation of the gases upon their subsequent in-excessive amounts in the beginningv and the rarefication in the fumigator. Therefore, being less volatile in excessive amounts at the end. mixed in the proper proportions in the accumu- Attempts have been made to remedy this situalater, the drop in pressure therein has no effect '30 1 .tion by the use of multiple hole inductor tubes, upon the proportions and the fumigator is always and while these have helped considerably, they supplied with precisely the desired ratio of vapors. by no means overcome the diiiiculty. The As an example of the invention, 6 lbs. of ethylchanges from the desired proportions will cause ene oxide and 54 lbs. of liquid carbon dioxide are very considerable variations in the efliciency of provided in a pressure tank, under a pressure of 35 the fumigation, and many fumigation failures are roughly 800 lbs. per square inch. These madirectly traceable to variations in the proportions terials are then vaporized into an accumulator of the constituents. having a capacity of in the neighborhood of 100 v Also in the case of liquids which may be more cubic feet. This will involve a reduction of pres- 40 or less completely miscible, removal of vapors in sure to about 75 lbs. The vapors are admitted to 40 the proportions in which the liquids are present the accumulator under afairly high pressure drop may be impossible or difficult, under present so that mixing is promptly and completely semethods, because the evaporation rates may not cured. When the entire quantity of liquid has correspond to the desired mixture. vaporized, the liquid tank may be disconnected.

5 By means of the present invention, vapors are If desired, more than one tank fullof liquid may supplied in exactly the predetermined and desired be vaporized into the accumulator. In each case proportions, and in perfectly homogeneous form. it is important to evacuate the entire container,

The invention is illustrated diagrammatically however. in the drawing, wherein is shown a liquid con- The vapors within the accumulator are pref- "30 tainer 2 from which the vapors may be removed erably heated to a temperature of 120 F. It has to the accumulator I. The mixed vapors from been discovered that by supplying the gases at this the accumulator are passed through the line 4 temperature the fumigation is considerably into the fumigator I. A vacuum pump 6 is proassisted. vided in order to evacuate the fumigator if de- The product to be fumigated, for instance to- 56 sired. The accumulator 3 is also provided with bacco, food products or the like, is then placed within the fumigator, which is closed and evacuated. Atter the desired degree of vacuum has beensecuredthemixedandheatedvaporsare thenadmittedtothetanhthepressurebeing raised thereby, and are held within the fumigator for the desired period, for example two or three hours.

The term "liquid", as used herein, denotes materiais of approximately liquid density, whether actually above or below the critical point.

The term immiscible", as used herein, denotes materials which are not completely miscible in the proportions in which they are used as fumi-.v

there is a division between the fumigating with said mixed vapors.

2. The method as set forth in claim 1, in which the liquids are present in the proportions of the order of 9 parts carbon dioxide to one part of ethylene oxide. v

3. The method of fumigating with mixtures of ethylene oxide and'carbon dioxide, which comprises expanding a liquid charge containing said ingredients in the desired proportions to completely gasiiy the same, retaining the completely gasifled charge in gasifled form until it becomes homogeneous, and subsequently. applying gas from the charge to the articles to be fumigated.

.4.-'ihemethcdotmmigatingwithmixtmesof ethylene oxide and'carbon dioxide, which comprises'chargingacontainerwiththeliquidingredients'in the proportions desired for fumi-' gating, expanding substantially the entire container charge into gaseous form. and retaining the expanded gaseous charge before application to the articles to be fumigated until it becomes entirely homogeneous in the gaseous form.

5'. The method of fumigating with mixtures of methyl formate and carbon dioxide, which comprises expanding a liquid charge containing said ingredients in the demred proportions to completely gasify the same, retaining the completely gasiiled charge in gasified form until it becomes homogeneous, and subsequently applying gas from the charge to the. articles to be i'umigated.

6. In'the fumigation of insect pests with a mixed vapor from a charge of liquid ethylene" oxide and carbon dioxide, the steps of completely volatilizing said liquids, thoroughly admixing the v vapors therefrom, heating said vapors to a tem perature of the order of 120 it, and introducing said heated vapors into a vacuum zone containing the material to be fumigated.

7. In the fumigation of insect pests with a liquid charge of ethylene oxide and carbon dioxide, the

steps of completely volatilizing said liquids thoroughly admixing the vapors therefrom, heating said vapors to a temperature of the order of 120 F. under a' pressure of 75 lbs., and introducing said heated vapors into a vacuum zone containingthe material to be fumigated.

8. The method'as set forth in claim 7, in which the vapors are collected under a pressure of the order 0M5 lbs. superatmospheric, and said fumigation is carried out under an air pressure of the order of inch of mercury.

JOHN in. mm 

